AC-3 Bitrate

Videoimpressions0622 wrote on 2/12/2008, 5:25 PM

I read somewhere that the standard bitrate for AC-3 encoded audio is 192Kbps. When rendering for DVD Architect from Vegas, then, should one render their AC-3 audio at this rate, or higher (and how high, too?)? Knowing this rate also is necessary when using a bitrate calculator, so the answer will help both DVD audio quality and determining overall bitrate so that the program fits on a 4.7 SS DVD, too!

Comments

owlsroost wrote on 2/13/2008, 10:48 AM

For DVD, normally it's 192 kbps for stereo and 448 kbps for 5.1

As far as know, 448 kbps is the recommended maximum for AC3 on DVD, since players are not required to support higher rates.

I don't know if you are allowed higher (up to 448 kbps) rates for stereo on DVD....

Tony

Videoimpressions0622 wrote on 2/13/2008, 11:26 AM

I could have sworn that I've seen 256kbps (Stereo) AC-3 on commercial disks. Can anyone corroborate this? Does everyone here use 192Kbps, then?

TGS wrote on 2/13/2008, 2:34 PM

I've used 320 kbps for stereo and even 384 kbps for stereo without problems on my 5 year old Toshiba DVD player. But I haven't done any testing with numerous players. In fact, you've sort of scared me with this info, as now I'm wondering if it will be a problem on other players. I assumed it was ok.
(they were my own music projects, not for sale)

owlsroost wrote on 2/13/2008, 3:40 PM

My understanding is that above 448 kbps the AC3 audio packets (frames?) are larger than the standard 'pack' size used on a DVD - some players can cope, others can't.

I think there was a commercial music DVD issued a little while ago with high bitrate (> 448) AC3 - and they found that some customers had problems playing it.....

Based on the above, I assume that high-bitrate stereo is OK, provided it's not above 448 kbps.

There's all sorts of AC3 encoding guidelines etc in the Dolby tech library [url=http://www.dolby.com/resources/tech_library/index.cfm]

A quote from the 'Dolby Digital Professional Encoding Guidelines' document - [url=http://www.dolby.com/assets/pdf/tech_library/46_DDEncodingGuidelines.pdf]:

"Dolby Laboratories recommends that all multichannel (more than two-channel) material is encoded at 448 kb/s and that all two-channel stereo content is encoded at 192 kb/s."

Tony